National Geographic radio spoke to Tim Samaras shortly before the storm chaser's death.

National Geographic storm chaser Tim Samaras gave an interview on the day of his death—speaking to National Geographic radio host Boyd Matson from the road on May 31 about his attempts to study twisters in the hopes of preventing death and devastation.

"[Scientists] know their topic and they're very passionate about what they do," said Justin O'Neill, a radio producer with National Geographic Weekend. "[However,] they're not always the most effusive."

Except for Samaras—he was a great guy with a good sense of humor, said O'Neill, who worked with Samaras several times. "I feel awful for his family, and I know that he'll be missed as an Explorer and colleague at National Geographic."

The following interview started at 12:45 p.m. EDT on the day Samaras died, ending around 1 p.m. EDT. It has been edited for length and content. According to reports, confirmed sightings of the tornado near El Reno, Oklahoma, occurred at 6:06 p.m. CDT.

Boyd Matson: This is National Geographic Weekend. I'm Boyd Matson. It's tornado season. The one person who knows as much as anyone about tornadoes is National Geographic grantee Tim Samaras, a storm chaser who is, right now, in his vehicle on the way from Kansas to Oklahoma because tornado season is still underway. Tim, welcome to the show.

Tim Samaras: Thanks for having me.

BM: Last year was kind of calm, but this year it's brought back in full force just how bad tornadoes can be, and they're frightening because you can see them coming but you're not exactly sure where they're going to hit.

TS: Yeah, that's correct. And actually, the season was quiet right up until about the middle of May, and it was like a switch that came on. And all of a sudden, tornadoes were just on an incredible rampage, certainly with Moore, Oklahoma, at the top of our minds.

BM: And of course, people like you, Tim, as we've seen over the years, you go out looking for tornadoes. I just saw a video you shot in May, standing outside your vehicle, looking up at the sky with a huge cloud. What convinces you that it's ok to get out and take pictures—that it won't make a sudden turn and come right toward you?

TS: Well, when you're out looking for these things, because they're so fleeting and unpredictable, there's always that chance. But I've been chasing these things for almost 30 years now. And not that I know exactly where they're headed and what they're doing, [but] I feel reasonably comfortable getting up close and personal so that we can collect measurements of these tornadoes.

And certainly the clip that you witnessed was during the final stages of a tornado that actually struck western Kansas. We're watching the demise of this tornado right in front of our eyes. We are watching some of the winds wrap and I can predict that the tornado is basically dissipating, so at that point we were safe to get out and really observe it.

BM: Does it seem that the force of these tornadoes, as weather patterns are changing, as climate is warming, does it seem that they're getting stronger? Are the conditions present to make the tornadoes more destructive than ever?

TS: Well, that's the part that's really tough to get a handle on, simply because we really don't have a very long time history to make comparisons.

What I have personally seen over the past 20 years is it appears that a lot of the tornado activity has shifted a little bit toward the north. It may be that the tornado season gets going a little earlier than usual, and then ends a little earlier.

Typically tornado season begins somewhere in April and tapers off in late June. And what we have been finding is basically a shift, perhaps closer to March and early April, and then tornado season comes to more of an abrupt end toward the end of June.

That wasn't necessarily true 20 years ago.

BM: One thing, though, when you're chasing storms, and you have a pretty good idea of how they're going to go, have you ever had one turn on you, Tim, and you just start to think, "We've got to get out of here"? In fact, don't I remember you once having your keys locked in the car when a tornado was coming your way?

TS: Well, you know, as a matter of habit, in some of these newer cars, if you don't set your system up right, you get out of your car, you slam the door shut, and then the door locks! So I have this habit, that every time I get out of my vehicle and there's a tornado in progress, I roll the window down. I think about that very thing, and the sheer panic, and if does happen, I'm quick to find a rock to get in.

BM: So you have had them turn on you.

TS: Tornadoes, I have had them turn, especially during what we call the "rope-out" stage, which is the end of their life. Because they wrap up in a very tight, high-velocity tornado that's on the ground and their paths are very, very unpredictable.

And I've seen them do a 360 or 180 and come right back at me. So we're really careful during the rope-out stage.

Now, when they're in what we call the mature stage, and the tornado is at its greatest strength, we find that the tornado actually tracks in more or less a straight line. That's not always the case, but the tornadoes that we have witnessed and we have actually deployed instruments on, they actually go in a pretty good straight line.

BM: All right, Tim, thanks for updating us on these devastating forces of nature, and we really appreciate the work that you're doing out there, trying to give us a better understanding of how they form, where they're coming, and reminding us, if you live in Tornado Alley, you better have a tornado shelter somewhere nearby.